One.relative_identifier(
  1 + 2,
  key: 3 + 4
) + Two.relative_identifier(
  2 + 1,
  key: 4 + 3
)
One.relative_identifier(
  1 + 2,
  key: 3 + 4
)(
  4 + 5,
  key: 6 + 7
) - Two.relative_identifier(
  2 + 1,
  key: 4 + 3
)(
  5 + 4,
  key: 7 + 6
)
One.relative_identifier key: 1 + 2
One.relative_identifier unqualified 1 + 2,
                                    key: 3 + 4
One.relative_identifier 1 + 2,
                        key: 3 + 4